Cutting elements are traditionally utilized for a variety of material removal processes, such as machining, cutting, and drilling. For example, tungsten carbide cutting elements have been used for machining metals and on drilling tools for drilling subterranean mining formations. Similarly, polycrystalline diamond compact (PDC) cutters have been used to machine metals (e.g., non-ferrous metals) and on subterranean drilling tools, such as drill bits, reamers, core bits, and other drilling tools. Other types of cutting elements, such as ceramic (e.g., cubic boron nitride, silicon carbide, and the like) cutting elements or cutting elements formed of other materials have also been utilized for cutting operations.
Drill bit bodies to which cutting elements are attached are often formed of steel or of molded tungsten carbide. Drill bit bodies formed of molded tungsten carbide (so-called matrix-type bit bodies) are typically fabricated by preparing a mold that embodies the inverse of the desired topographic features of the drill bit body to be formed. Tungsten carbide particles are then placed into the mold and a binder material, such as a metal including copper and tin, is melted or infiltrated into the tungsten carbide particles and solidified to form the drill bit body. Steel drill bit bodies, on the other hand, are typically fabricated by machining a piece of steel to form the desired external topographic features of the drill bit body.
In some situations, drill bits employing cutting elements may be used in subterranean mining to drill roof-support holes, face holes, blast holes, degassing holes, etc. For example, in underground mining operations, such as coal mining, tunnels must be formed underground. In order to make the tunnels safe for use, the roofs of the tunnels must be supported in order to reduce the chances of a roof cave-in and/or to block various debris falling from the roof. In order to support a roof in a mine tunnel, boreholes are typically drilled into the roof using a drilling apparatus. The drilling apparatus commonly includes a drill bit attached to a drilling rod (commonly referred to a “drill steel”). Roof bolts are then inserted into the boreholes to support the roof and/or to anchor a support panel to the roof. The drilled boreholes may be filled with a hardenable resin prior to inserting the bolts, the bolts may have self expanding portions, or the bolts may be secured directly into the rock in order to anchor the bolts to the roof. Support bolts may also be utilized to secure other portions of a mining tunnel, such coal ribs/pillars, side faces, and floors.
Various types of cutting elements, such as PDC cutters, have been employed for drilling boreholes for roof bolts. Although other configurations are known in the art, PDC cutters often comprise a substantially cylindrical or semi-cylindrical diamond “table” formed on and bonded under high-pressure and high-temperature (HPHT) conditions to a supporting substrate, such as a cemented tungsten carbide (WC) substrate.
During drilling operations, heat may be generated in the cutting elements due to friction between the cutting elements and a mining formation being drilled. Additionally, the cutting elements may be subjected to various compressive, tensile, and shear stresses as the cutting elements are forced against rock material during drilling operations. The combination of stresses and/or heat may cause portions of cutting elements to become worn and/or damaged from drilling. For example, portions of a cutting element that come into forceful contact with a rock formation during drilling may experience spalling, chipping, and/or delamination, decreasing the cutting effectiveness of the cutting element. Often, cutting elements and drill bits are disposed of when cutting portion of the cutting elements mounted to the drill bits become excessively worn and/or damaged.
Additionally, the combination of stresses and/or heat generated during drilling may cause cutting elements to become dislodged from drill bits. For example, stresses and heat may weaken a braze joint holding a cutting element to a bit body, resulting in displacement of the cutting element from the bit body. Such problems may cause delays and increase expenses during drilling operations. Avoiding such delays may reduce unnecessary downtime and production losses, which may be particularly important during bolting operations in mine tunnels due to various safety hazards present in these environments.